Eyeglass designers have been making continuous efforts in designing a great variety of eyeglasses to satisfy consumers' needs and tastes. Eyeglasses can alleviate eye defects such as myopia, hyperopia or astigmatism, or protect the eyes against bright daylight and ultraviolet light from the sun, and hence have become an essential product in daily life. Being worn on the face, it is often desirable that the design of eyeglasses are aesthetically pleasing. Eyeglasses also serve as a fashion accessory and even form part of the identity of some celebrities. The ornamentation of eyeglasses are available in a wide range of styles, materials, premium designs, and further decorated with a selection of colors and patterns in the frames, including temples, eyeglass fronts, rims and bridges, to meet the preference of different consumers.
Conventionally, the decorative designs are two dimensional patterns or graphics. To produce eyeglass frames with decorative patterns, such patterns are usually transferred on to the surface materials, and further coated with a protective plastic layer. Because the protective layer can be worn out after prolonged use, ultimately the transferred patterns will also be depleted.
Accordingly, laminate material for eyeglass frames were developed and manufactured by the following known method in which a first plastic sheet is first pasted with a glue layer, which is then printed with desired patterns by silk screen printing. The intermediate laminate is pasted with another glue layer and glued to a second plastic sheet, and subsequently adhered together by hot compression. The resulting laminate has decorative patterns embedded between the two plastic sheets and is difficult to wear out during use. However, the relevant configuration and manufacturing process of such a laminate is complex, and has a lengthy production cycle. Further, a different silk screen is required if a different pattern is to be printed, resulting in low productivity and high manufacturing cost.
Cellulose Acetate is one of the most common thermoplastic materials used in making eyewear. It allows patterns to be transferred on thermoplastic sheets and overcomes the limitation for injection plastics.
In conventional technologies, eyeglass thermoplastic sheeting has to be coated with a glue layer, and then printed with patterns by silk screen printing. When the ink dries up, another glue layer will be coated and adhered to a second plastic sheet by compression or thermal process. These techniques however are costly and time consuming, especially for producing polychrome patterns.
Silk screen printing requires one mask for each monochrome and only one monochrome can be printed at each time. In addition, to manufacture products with different patterns, a different set of silk screens is required. It also takes a long time to verify the silk screen pattern and the effect on sheet material, resulting in an extended production cycle. Furthermore, the pattern cannot be very fine because the ink is applied to the back of the image carrier and pushed through porous or open areas.
The conventional method is also limited to producing two dimensional patterns or graphics.
A thermoplastic laminate printed with internal decorative patterns for eyeglass frames and its manufacturing process has been disclosed in patent publication nos. WO2007/128196 and U.S. Ser. No. 11/734,903. However, the referenced manufacturing process is, due to the complexity, done manually, thus resulting in a lengthy production cycle. Furthermore, the stability of the eyewear is limited and the uniformity as well as the dimension of the eyewear cannot be easily controlled based on such manufacturing process, resulting in low productivity and high manufacturing cost with poor aesthetic. A further consequence of the poor stability is that internal stresses may be set up in the frame, which are self relieved over time. As the frame relaxes naturally this can cause the lens to deform affecting its corrective power.
Consequently, there is a need to produce eyewear with good stability and with high density and durable decorative patterns. There is also a need to improve the current manufacturing process to produce eyewear with a good uniformity in profile and dimensions.